


territorial

by kinkykawa



Series: youngblood (miyacest one-shots) [3]
Category: Haikyuu!!
Genre: (neither endgame nor a couple tho), Biting, Come Marking, Incest, Intercrural Sex, Jealous Osamu, Jealousy, M/M, Marking, Possessive Behavior, Possessive Sex, Post-Canon, Rough Sex, Sibling Incest, Twincest, implied Sakusa/Atsumu, miyacest
Language: English
Status: Completed
Published: 2020-07-16
Updated: 2020-07-16
Packaged: 2021-03-05 00:13:52
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,777
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25315135
Author URL: https://archiveofourown.org/users/kinkykawa/pseuds/kinkykawa
Summary: Atsumi ishis, after all, was born with him and for him. Osamu was born already waiting for Atsumu to follow. He’d existed only twelve minutes without Atsumu in this world. They belong to each other. They’ve never doubted that.They belong to each other, he knows. But it doesn’t hurt to remind each other of that.
Relationships: Miya Atsumu/Miya Osamu
Series: youngblood (miyacest one-shots) [3]
Series URL: https://archiveofourown.org/series/1933474
Comments: 2
Kudos: 469





	territorial

**Author's Note:**

> prompted by matsumu, who asked for jealous and possessive osamu who sees atsumu hanging around with sakusa a lot and "flirting" with him a little, and after confronting atsumu about it, fucks his twin 👀 i tweaked it just a little bit to be more fun. carries the same vibes as "fundamentals" and "eavesdropper"!! 
> 
> mostly beta'd, but will fix any mistakes if i catch any later on. now let us all join hands, face our gods, and yeet backwards into hell together bc hell is more fun.

Atsumu talks about Sakusa a lot.

Granted, Atsumu talks about his teammates a bunch in general — rants about Bokuto’s antics during games and practice; complaints that Meian is too strict or not strict enough; long-winded explanations of plays he wants to try with Hinata or Oliver. And though Osamu would never admit it out loud, he likes that Atsumu still talks volleyball with him, that his twin has never withheld discussions of the sport out of misguided pity or restraint. Osamu may not play anymore, but he’s never stopped loving volleyball.

But Sakusa—

Sakusa feels different.

The way Atsumu complains about Sakusa is different, calling him things like a _too-blunt jerk_ or a _prickly bastard._ The way he refers to Sakusa is different, too, always _Omi-kun_ and _Omi-omi._ And the way he discusses Sakusa and volleyball—

Osamu has always known that Sakusa is a brilliant player. And unlike other spikers, other aces — Ushijima, Hoshiumi, Bokuto; even Hinata — Sakusa does not command attention, doesn’t take up the whole court with an overwhelming presence. His style of play is straightforward, neat, and unflashy. His strength is his simplicity. He wins because he makes the effort to follow through each play and fulfill his role on the court. Those bendy fucking wrists of his are just a bonus.

Osamu has also always known Atsumu’s fascination with Sakusa. He remembers Atsumu coming home from that first youth training camp, and a rivalry that bloomed where least expected. Kageyama might be Atsumu’s adversary as a setter, and Hinata might be the perfect challenge on the court, but Sakusa—

Sakusa feels different.

So if Osamu lingers a little longer around his brother while they’re both at home in their tiny shared apartment; if he’s softer around the edges sometimes when he doesn’t mean to be; if he fucks Atsumu a little rougher in bed, well. He doesn’t think he can be blamed for it.

(Atsumi is _his,_ after all, was born with him and for him. Osamu was born already waiting for Atsumu to follow. He’d existed only twelve minutes without Atsumu in this world. They belong to each other. They’ve never doubted that.)

Whatever jealousy exists inside Osamu, though, he’s usually careful to keep buried. He shoves it between his ribs and leaves it there, pruning its roots so it doesn’t dig too deep. He knows: he’s the one Atsumu comes home to. He’s the one who wakes up with Atsumu beside him, all ridiculous bedhead and sleep-scrunched eyes. He’s the one with whom Atsumu is vulnerable and bratty; the one who knows Atsumu for all his cruelty and vindictiveness and insatiable curiosity. He’s the one, the _only_ one, who gets to press Atsumu down to the bed, mouth everywhere over skin, toying with him until he’s a desperate, shivering wreck.

He’s the one against whom all of Atsumu’s bright and ragged edges fit.

But then Osamu sees Atsumu smiling at Sakusa after practice, during a game — sees the way Sakusa starts letting Atsumu _touch_ him — sees how the two of them start falling into orbit around each other — and the roots start to creep a little tighter around his chest.

They belong to each other, he knows. But it doesn’t hurt to remind each other of that.

Things crack open just a little on a Saturday.

Several of the Black Jackals are at the onigiri shop for the evening, having dinner after training. It’s nothing new; plenty of them come here, in groups or alone, with each other or with friends. Post-practice or post-game dinners are a regular occurrence, enough that Osamu knows their favorite orders by heart.

What _is_ different, though, is Atsumu sitting with Sakusa, at the far end of the counter instead of his usual spot near the corner. They’re talking about something Osamu can’t hear, mostly because Bokuto and Hinata are trying to tell him about how Inunaki rolled into the net pole during training. And Osamu _is_ trying to pay attention, to laugh and react in the right places, but his eyes keep wandering to blonde hair near black curls. And then Atsumu’s laugh rings out, and Osamu looks over to watch as his twin doubles over, hand pressed to his mouth, and Sakusa—

Sakusa turns away, but Osamu can see the corners of his mouth curl up in a little smile.

“Hey, Myaa-sam,” Bokuto pipes up innocuously, “you’re squishin’ the food.”

Osamu blinks, then glances down. He’s clamped down too hard on the onigiri he’s forming; the rice and minced pork have spilled between his fingers. He drops the sticky mess down to the counter, shaking his hands with a grimace.

“My bad,” he says, deliberately turning away to rinse his hands in the sink. “Got a little distracted.”

“Can we still eat that?” Hinata asks, peering over the counter.

“Hey, no fair, that was supposed to be mine,” Bokuto argues.

“It wouldn’t be formed into a ball anymore, though,” Tomas points out, fingers curled around his chin.

“Please,” Meian says, in a long-suffering tone, “just eat so we can go home.”

Osamu rearranges his face into a fond and exasperated smile when he heads back to the counter, shaking his head. But before he can reply, he glances sideways again, and this time he finds Atsumu looking right back at him with a little smile on his face.

 _Gotcha,_ his twin mouths, cheeky, and Osamu’s jaw clenches to stop himself from replying.

Oh that fucking _brat._

Atsumu lingers after everyone’s left, as he always does. He waits at the counter while Osamu finishes closing the shutters and doors, scrolling through something on his phone. When Osamu finally dims the lights inside, he turns around and smiles, expression like butter wouldn’t melt.

For a still-beat moment, the two of them just look at each other.

“Get up,” Osamu tells him, and Atsumu grins as he obliges.

He’s halfway out of his seat when Osamu crowds against him, pressing him up against the counter and biting down on his shoulder. Atsumu hisses, jerking slightly under his twin as he fumbles to catch his weight. Osamu is merciless from the get-go, digging fingers into Atsumu’s hips as he sucks at the skin exposed by Atsumu’s low collar, putting all the frustration of the last several days into the force of his teeth.

“Easy—” Atsumu starts, then falters with a gasp as Osamu grinds his hips against his twin’s ass. “Shit, _‘Samu,_ easy—”

“You,” Osamu murmurs, shoving his hands up Atsumu’s shirt to pinch his nipples, “don’t get ta tell me to go _easy._ ”

Any protest that Atsumu might have made gets cut off as Osamu pulls back, dragging his nails over Atsumu’s ribcage as he goes. He yanks Atsumu’s shirt off, throwing it somewhere nearby, then digs out the tiny packet of lube that’s predictably in his twin’s pocket. Foil packet acquired, he wrestles Atsumu’s jeans and boxers halfway down his thighs, exposing his ass and trapping his legs together. Then he works his own pants open enough to free his cock. He doesn’t have the patience to prep Atsumu, work him open until he’s writhing and begging, not right now. Instead, Osamu rips the packet open with his teeth and spills it over his hand, barely flinching at the sticky, cool sensation.

“Did you think about it?” he asks quietly, teasing along the curve of Atsumu’s ass.

“Think about wh—” Atsumu cuts off again when Osamu bites his neck.

“Him,” Osamu murmurs, brushing his lips over the mark he’s left. “You. This.”

He feels more than hears Atsumu’s huffed laughter, pressed close like this. “And if I have?”

There’s a pause, then Osamu sinks his teeth back into Atsumu’s shoulder in the same moment he shoves his hand between Atsumu’s thighs, slicking them up something messy. He relishes the surprised, shuddering yelp it draws from his twin, smirking as he smears lube over Atsumu’s skin, getting him nice and wet. Then he gets his hand around his own cock, stroking himself to full hardness, enjoying the way Atsumu shivers at the motions.

“No one else,” he says, lining himself up between Atsumu’s legs. “I ain’t ever letting anyone else get you like this.”

The pressure of Atsumu’s thighs isn’t anywhere near as tight as his ass, but it still feels delicious. Atsumu’s skin is warm and slick, and every thrust nudges his cock against the base of Atsumu’s own. And then there’s the _sounds_ his twin is making, needy whimpers and little half-gasps, loud in the emptiness of the shop.

“‘Samu,” Atsumu whines, squeezing his legs together more, “‘Samu — not enough — come _on,_ please, lemme—”

It sends a little thrill through Osamu, seeing and hearing his twin like this. He knows it’s not enough, of course; knows that he’s getting all the pleasure while Atsumu’s cock hangs neglected, aching to be touched. But Atsumu — pretty little brat that he is — won’t touch himself, will keep his hands braced against the counter while Osamu fucks him. Because Osamu hasn’t given him permission, because Osamu hasn’t said he can; because he knows exactly how Osamu wants him.

God, Osamu could drown in this — them, together, just like this.

“No,” he bites out, winding one arm around Atsumu’s waist to splay his hand at the base of Atsumu’s throat. “No, I’m gonna fuck ya, just like this. I’m gonna leave ya all sticky and _covered_ in a mess, and you’re gonna let me. And then I’m gonna take you back home and fuck you all over again, and _then_ you can come.”

“ _‘Samu,_ ” Atsumu half-sobs, but his hands don’t move. He stays there and lets Osamu fuck him, _take_ him, and the thought of all this being _for him_ pushes Osamu to the edge. A few more thrusts and he’s coming, painting Atsumu’s thighs in sticky white as he presses fingers into Atsumu’s skin hard enough to bruise, muffling his shout in his twin’s shoulder.

For a few moments, Osamu lets himself linger in this — the feeling of them pressed together, skin warm and damp with sweat, Atsumu trembling ever so slightly in his arms. Then he yanks himself back, reaching for a napkin from the counter to clean himself up, then tucking himself back in his pants.

“Get dressed,” he tells Atsumu, voice hoarse. “Sooner we get home, sooner I can wreck ya.”

Atsumu laughs under his breath as he shakily pulls his pants and underwear back up. He turns around to look for his shirt, but before that, trembling and eager hands reach out to tug Osamu in for a deep, hungry kiss. When they break apart, Atsumu’s smiling in full cat-canary satisfaction.

“Lookin’ forward to it.”

**Author's Note:**

> AYT if u guys wanna request more miyacest or just talk about this and other problematic things, come hit me up on twitter at [@kinkykawa_](https://twitter.com/kinkykawa_)!!!!


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